The present invention relates to a metal chelated azo dyestuff for inkjet recording, a recording liquid and recording liquid for inkjet containing the dyestuff and an inkjet recording method using the dyestuff. More particularly, the present invention relates to a metal chelated azo dyestuff for inkjet recording which can be preferably used as a black dyestuff in inkjet recording, a recording liquid for inkjet and an inkjet recording method.
A so-called inkjet recording method which allows droplets of a recording liquid containing water soluble dyestuffs such as direct dye and acidic dye to be ejected from a minute ejection orifice to effect recording has been put to practical use. The recording liquid for use in the inkjet recording method requires that it be able to be ejected over an extended period of time. The recording liquid also requires that it be fixed rapidly on PPC (plain paper COPIA) paper such as electrophotographic paper and fanhold paper (recording paper widely used for general official purposes such as continuous paper for computer, etc.) and give a printed matter having a good print quality, i.e., print having a definite contour free of running. The recording liquid further requires that it exhibit an excellent storage stability as a recording liquid. Accordingly, the solvent which can be used in the recording liquid is remarkably limited.
On the other hand, the dyestuff for recording liquid requires that it has a sufficient solubility in the solvent thus restricted and remain stable even after prolonged storage in the form of recording liquid. The dyestuff for recording liquid also requires that it gives a printed image having a high density and an excellent water resistance and light-fastness. However, it was difficult to meet these many requirements at the same time.
Further, the inkjet recording has been recently required to have adaptability to printing photo-like image, graphic image or the like (hereinafter abbreviated as xe2x80x9cphotographic imagexe2x80x9d) which is drastically improved as compared with the conventional inkjet recording. The black recording liquid for use in the printing is required to have further improvement in achromaticity of printed image. Further, unlike the letter printing involving printing with a density of 100%, the photographic image often employs so-called halftone printing involving 80% halftone dot meshing printing or 70% halftone dot meshing printing. In this printed area, the color of printed matter is gray rather than black. Therefore, the delicate hue of dyestuff which is not highlighted in 100% solid printed area, i.e., black printed area becomes highlighted.
In order to numerically express the achromaticity of the halftone area, halftone dot meshing printing is effected with a black ink at an arbitrary print density of from 0% to 100%, e.g., 80% using, e.g., xe2x80x9chalftone dot meshing functionxe2x80x9d of a commercially available graphic software or word processing software. The printed matter thus obtained may be measured for saturation (C* value) by means of a commercial colorimeter. C* is an index indicating the saturation of color of image. In the case of black image, as C* value is closer to zero, it indicates that the color of the image is a pure black or gray having less color hue to advantage. In order to give a satisfactory inkjet recorded image, it is desired that C* value of a halftone dot meshing image printed at a density of 80% which normally looks a dark gray be not greater than 8, preferably not greater than 7.5, more preferably not greater than 7, particularly not greater than 4.
However, it has heretofore been extremely difficult to obtain a pure black free of delicate hue such as greenish, reddish and bluish hues, i.e., achromatic black image over a wide print density range from light to dark color using a single dyestuff. In other words, when an image subjected to halftone dot meshing printing at a density of 80% in the same manner using a single dyestuff which is normally used in inkjet recording is measured for saturation, C* value thus measured is from 10 to 15 or about 20 in the extreme case. Accordingly, a gray image which is not required to have color tone looks bluish, brownish or reddish.
Therefore, in general, a black inkjet recording liquid which contains a plurality of dyestuffs incorporated therein in combination to compensate deviation of color tone is used. However, this black inkjet recording liquid is disadvantageous in that different dyestuff molecules excessively prevent the agglomeration of the other dyestuff particles and catalytic fade causes deterioration of light-fastness.
On the other hand, in order to embody a highly fine and highly sharp image during IJ recording, particularly photographic image printing, a dedicated coated paper, dedicated glossy paper, etc. (hereinafter abbreviated as xe2x80x9cdedicated paperxe2x80x9d) is used. However, when printed on recording media normally called photographic glossy paper, paper dedicated for inkjet, etc., the dyestuff tends to be acceleratedly decomposed under light due to the action of silicon oxide, aluminum oxide and a waterproofing agent such as polyamine which have been incorporated therein to form a highly fine and highly sharp image. As a result, when the photographically printed image obtained by inkjet recording method is posted indoor or outdoor, it can be easily discolored to disadvantage.
The light-fastness of an image can be numerically expressed as, e.g., discoloration value (xcex94E) determined by measuring the image which has been subjected to photo-deterioration acceleration test involving irradiation with, e.g., xenon arc light for degree of image discoloration from the initial value by means of a color difference meter. In order to provide a photographic image formed on dedicated paper by inkjet printing with a sufficient light-fastness, a black image having xcex94E value of about 10 or less after 80 hours of irradiation with xenon arc light is required. However, the conventional dyestuffs can difficultly provide 100% solid printed area with the aforementioned desired light-fastness. Further, the conventional dyestuffs show more remarkable image discoloration due to light, often as extremely great as from 20 to 50 as calculated in terms of xcex94E value, in a so-called halftone area such as 80% halftone dot meshing-printed area and 70% halftone dot meshing-printed area, which is often used in photographic image printing.
In an attempt to improve the achromaticity and light-fastness of a black image at the same time, various dyestuffs and recording methods have heretofore been proposed. However, a dyestuff has never been developed which meets sufficiently the aforementioned complicating and growing need of the market and can be easily prepared.
In general, a black recording liquid contains a disazo dyestuff, a trisazo dyestuff or a polyazo dyestuff containing more azo groups. These dyestuffs are used to form the aforementioned purer black, i.e., achromatic black image. However, this type of a dyestuff can difficultly meet the recent requirement for strict light-fastness, especially on dedicated paper.
In addition, the aforementioned requirement for achromaticity cannot be attained by the conventional polyazo dyestuffs such as disazo and trisazo dyestuffs. Therefore, it has been often practiced to adjust the color hue to higher achromaticity by using a complementary color or using a plurality of black dyestuffs in combination. As a result, the light-fastness, which is now insufficient, tends to be deteriorated more and more.
On the other hand, in an attempt to embody an sufficiently light-fast image, the application of an existing or novel metal chelated azo dyestuff which is considered excellent in light-fastness has been studied. For example, Japanese Patent Laid-Open No. 1990-75672 discloses that a metal chelated dyestuff is used for inkjet recording and exemplifies metal chelated dyestuffs having the following structures. Although these metal chelated dyestuffs have an improved light-fastness, they tend to have bluish tone and thus cannot sufficiently meet the recent need from the standpoint of achromaticity. 
An aim of the present invention is to provide a dyestuff and recording liquid which allows recording with a sufficient light-fastness and a saturation that is low enough to give a desirable black tone even when subjected to inkjet recording on, e.g., dedicated paper as recording or writing utensils and a recording method using this recording liquid.
As a result of studies, the inventors found a dyestuff having a special structure having properties accomplishing the aforementioned aim and then worked out the present invention. The inventors confirmed that the use of a specific compound having a specific form of polyazo compound coordinated to a metal as ligand makes it possible to obtain an achromatic (close to ideal black) dyestuff having a high light-fastness and the use of this dyestuff makes it possible to obtain a recording liquid which can sufficiently meet the aforementioned market need for inkjet recording that sufficiently desirable achromaticity and light-fastness can be met at the same time even when printed on dedicated paper at a low density in the form of halftone. The present invention has thus been worked out.
It was further found that the aforementioned dyestuff can provide an excellent recording liquid which can keep a high light-fastness even when a complementary dyestuff is incorporated therein for toning.
In other words, the subject matter of the present invention lies in a metal chelated azo dyestuff for inkjet recording the free acid form of which is represented by the following general formula (1) or (1xe2x80x2), a recording liquid and a recording liquid for inkjet containing the metal chelated azo dyestuff and an inkjet recording method using the metal chelated azo dyestuff: 
(wherein the general formula (1) represents a compound having at least one or more hydrophilic group per molecule; M represents an arbitrary metal; A, B and C each independently represents an aromatic ring which may have arbitrary substituents; D represents an aromatic ring which may have arbitrary substituents other than azo group; m represents an integer of 0 to 1; n represents an integer of from 0 to 3; p represents an integer of from 0 to 2; q represents an integer of from 1 to 3, with the proviso that if there are a plurality of B""s, they may be the same or different; R1 and R2 each independently represents hydrogen atom or arbitrary substituent; M can take tridentate or higher coordination in which M may take arbitrary ligand-to-metal coordination at arbitrary substituent or bond in the general formula (1) or with arbitrary ligands; and a metal ion may be further coordinated to A and B, B and B which are adjacent to each other with an azo group interposed therebetween if there are a plurality of B""s or B and C in the form of xe2x80x94Oxe2x80x94Mxe2x80x94Oxe2x80x94), 
(wherein the general formula (1xe2x80x2) represents a compound having at least one or more hydrophilic group per molecule; M represents an arbitrary metal; A, B and C each independently represents an aromatic ring which may have arbitrary substituents; D represents an aromatic ring which may have arbitrary substituents other than azo group; m represents an integer of 0 to 1; n represents an integer of from 0 to 3; p represents an integer of from 0 to 2; q represents an integer of from 1 to 3, with the proviso that if there are a plurality of B""s, they may be the same or different; R1 and R2 each independently represents hydrogen atom or arbitrary substituent; and M can take tridentate or higher coordination in which M may take arbitrary ligand-to-metal coordination at arbitrary substituent or bond in the general formula (1) or with arbitrary ligands).
Further, the subject matter of the present invention lies in a recording liquid containing an aqueous medium, i) at least one black metal chelated azo dyestuff the free acid form of which is represented by the following general formula (8) or (8xe2x80x2) and ii) at least one or more other water soluble dyestuff and an inkjet recording method: 
(wherein the general formula (8) represents a compound having at least one or more hydrophilic group per molecule; M1 represents an arbitrary metal; A1, B1 and C1 each independently represents an aromatic ring which may have arbitrary substituents; D1 represents an aromatic ring which may have arbitrary substituents other than azo group; m1 represents an integer of 0 to 1; n1 represents an integer of from 0 to 3; p1 represents an integer of from 0 to 2; q1 represents an integer of from 0 to 3, with the proviso that if there are a plurality of B1""s, they may be the same or different; R13 and R14 each independently represents hydrogen atom or arbitrary substituent; M1 can take tridentate or higher coordination in which M1 may take arbitrary ligand-to-metal coordination at arbitrary substituent or bond in the general formula (8) or with arbitrary ligands; and a metal ion may be further coordinated to A1 and B1, B1 and B1 which are adjacent to each other with an azo group interposed therebetween if there are a plurality of B1""s or B1 and C1 in the form of xe2x80x94Oxe2x80x94Mxe2x80x94Oxe2x80x94), 
(wherein the general formula (8xe2x80x2) represents a compound having at least one or more hydrophilic group per molecule; M1 represents an arbitrary metal; A1, B1 and C1 each independently represents an aromatic ring which may have arbitrary substituents; D1 represents an aromatic ring which may have arbitrary substituents other than azo group; m, represents an integer of 0 tot; n1 represents an integer of from 0 to 3; p1 represents an integer of from 0 to 2; q1 represents an integer of from 0 to 3, with the proviso that if there are a plurality of B1""s, they may be the same or different; R13 and R14 each independently represents hydrogen atom or arbitrary substituent; and M1 can take tridentate or higher coordination in which M1 may take arbitrary ligand-to-metal coordination at arbitrary substituent or bond in the general formula (8xe2x80x2) or with arbitrary ligands).
In the specification of the present application, among the metal chelated azo dyestuffs the free acid form of which is represented by the general formula (1) or (8), those excluding embodiments in which a metal ion may be further coordinated to A1 and B1, B1 and B1 which are adjacent to each other with an azo group interposed therebetween if there are a plurality of B1""s or B1 and C1 in the form of xe2x80x94Oxe2x80x94Mxe2x80x94Oxe2x80x94 are defined as a metal chelated azo dyestuff represented by the general formula (1xe2x80x2) or (8xe2x80x2), respectively.
The present invention will be further described hereinafter.
The dyestuff of the present invention is represented by the aforementioned general formula (1). The dyestuff represented by the general formula (1) is a trisazo compound or a polyazo compound having more azo groups which is a complex compound of a molecule having a phenol, naphthol or analogous hydroxyl group-containing aromatic ring incorporated therein at ends of a chain of aromatic rings connected with an azo group with an arbitrary metal. The metal chelated azo dyestuff of the present invention is a triazo or higher metal chelated dyestuff having substituted amino groups on the aromatic ring at right end.
The dyestuff of the present invention preferably has a molecular weight of not greater than 5,000, particularly not greater than 2,000.
The dyestuff represented by the general formula (1) is a water soluble dyestuff and has at least one or more hydrophilic group per molecule to have water solubility. Such a hydrophilic group is not specifically limited so far as it is a water soluble hydrophilic group which is commonly used as an inkjet recording liquid. Examples of the hydrophilic group include sulfonic acid group, carboxylic acid group, phosphoric acid group, etc. Preferred among these hydrophilic groups are sulfonic acid group and carboxylic acid group. The dyestuff of the general formula (1) wherein the number of hydrophilic groups is from 2 to 6 as a whole is suitable for properties of inkjet recording liquid.
In the dyestuff represented by the general formula (1) of the present invention, A, B, C and D each independently represents an arbitrary aromatic ring. At least one of A, B, C and D may have hetero rings. In order to optimize the properties of the dyestuff, the aromatic rings described as A, B, C and D may be substituted by arbitrary substituents properly selected depending on the purpose of the dyestuff. A, B, C and D each is preferably a benzene ring which may be substituted or a naphthalene ring which may be substituted. In particular, B and D each is preferably a naphthalene ring which may be substituted.
The proper substituents which A, B and C respectively have depending on the purpose of the dyestuff are not specifically limited. The substituents on D are not specifically limited so far as they are not azo groups.
In some detail, the substituents on A are preferably at least one or more substituent selected from the group consisting of halogen atom, phosphono group, sulfonic acid group, carboxyl group, hydroxyl group, nitro group, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, alkoxy group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, amino group which may be substituted, acylamino group which may be substituted, sulfonylamino group which may be substituted, phenylazo group which may be substituted and naphthylazo group which may be substituted.
The substituents on B are preferably at least one or more substituent selected from the group consisting of halogen atom, phosphono group, sulfonic acid group, carboxyl group, hydroxyl group, nitro group, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, alkoxy group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, amino group which may be substituted, acylamino group which may be substituted and sulfonylamino group which may be substituted.
The substituents on C are preferably at least one or more substituent selected from the group consisting of halogen atom, phosphono group, sulfonic acid group, carboxyl group, hydroxyl group, nitro group, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, alkoxy group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, amino group which may be substituted, acylamino group which may be substituted and sulfonylamino group which may be substituted.
In particular, in the case where at least one of A, B and C rings has substituents, the substituents are preferably those selected from the group consisting of halogen atom, sulfonic acid group, carboxyl group, hydroxyl group, nitro group, alkyl group which may be substituted, alkoxy group which may be substituted, amino group which may be substituted, acylamino group which may be substituted and sulfonylamino group which may be substituted.
D may be further substituted by substituents other than those defined in the general formula (1), but azo groups are not directly connected to D ring. The substituents on D are preferably at least one substituent selected from the group consisting of halogen atom, carboxyl group, hydroxyl group, nitro group, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, alkoxy group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, amino group which may be substituted, acylamino group which may be substituted, sulfonylamino group which may be substituted, alkoxycarbonyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted and aminocarbonyl group.
In the case where A to D have substituents which further have substituents, the substituents each normally has from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms.
The dyestuff represented by the general formula (1) of the present invention is synthesized by a method known per se [see e.g., Yutaka Hosoda, xe2x80x9cShinsenryou Kagaku (New Dye Chemistry)xe2x80x9d, Gihodo, Dec. 21, 1973, pp. 396-409] via diazo forming step and coupling step.
The dyestuff represented by the general formula (1) can be obtained, e.g., by converting an aromatic amine having a partial structure A to a diazo form, condensing the diazo compound to an aromatic amine having a partial structure B, further converting the compound thus obtained to a diazo form, condensing the diazo compound to an aromatic amine having a partial structure C, further converting the compound thus obtained to a diazo form, and then condensing the diazo compound to an aromatic compound having a partial structure D, i.e., by allowing a desired metal salt to act on a compound obtained by the successive repetition of conversion to diazo form and condensation.
Examples of the aromatic amine containing A as a partial structure include aromatic amines such as 4-nitroaniline, 2,6-dichloro-4-nitroaniline, 2-cyano-4-nitroaniline, 4-chloroaniline, sulfanilic acid, 2-aminobenzene-1,4-disulfonic acid, C acid, Dahl acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 3-aminophenylphosphoric acid, 2-aminoterephthalic acid, 3-aminoisophthalic acid, 2,5-diaminobenzoic acid and 5-amino-2-nitrobenzoic acid, heterocyclic aromatic amines such as 2-amino-3-aminocarbonyl-5-formylthiophene, 2-amino-6-carboxybenzothiazole, 2-amino-6-sulfo-benzothiazole, 2-amino-4,5-dicyanoimidazole and 2-amino-4,5-dicarboxyimidazole, and derivatives thereof.
Examples of the aromatic amine containing B as a partial structure include aromatic amines such as 1-naphthylamine, 1,6-Cleve""s acid, 1,7-Cleve""s acid, 2-methoxyaniline, 2-ethoxyaniline, 2-amino-paracresidine, 2,5-dimethoxyaniline, 2,5-diethoxyaniline and 5-acetylamino-2-methoxyaniline, heterocyclic aromatic amines such as 2-amino-3-cyanothiophene, and derivatives thereof.
Examples of the aromatic ring containing C as a partial structure include aromatic amines such as 8-amino-7-hydroxy-2-naphthalenesulfonic acid, 2-hydroxyaniline, 2-hydroxy-5-methylaniline, 2-hydroxy-5-methoxyaniline, 2-hydroxy-5-ethoxyaniline and 5-acetylamino-2-hydroxyaniline, etc. These aromatic amines may be obtained by subjecting a precursor having a hydroxyl moiety in the form of alkoxy which interacts with a metal to the aforementioned successive repetition of diazo formation and condensation, and then allowing a metal salt and a proper amine to act on the product so that the alkoxy group is converted to a hydroxyl group coordinated to metal.
Examples of the aromatic compound containing D as a partial structure include xcex1-naphthol derivatives such as Shoelkoft acid, Videt acid, L acid, chromotropic acid, Nevile-Winter""s acid and xcex5 acid, amino-xcex1-naphthol derivatives such as xcex3 acid, phenyl xcex3 acid, 3-sulfophenyl xcex3 acid, 4-carboxyphenyl xcex3 acid, RR acid, J acid, phenyl J acid, methyl J acid, di-J acid, carbonyl J acid, H acid, benzoyl H acid, phenylsulfonyl H acid, M acid, S acid, SS acid and K acid, xcex2-naphthol derivatives such as R acid, G acid, Crocein acid, Schaffer""s acid, F acid, oxynaphthoic acid and 3-hydroxy-1,8-naphthalic acid, amino-xcex2-naphthol derivatives such as Boeniger acid, heterocyclic aromatic compounds such as 8-hydroxy-5-sulfoquinoline, etc. Preferred among these aromatic compounds are J acid, xcex3 acid, RR acid, 4-carboxyphenyl gamma acid, and 3-sulfophenyl gamma acid.
In the dyestuff represented by the general formula (1) of the present invention, R1 is preferably a hydrogen atom, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, phenyl group which may be substituted, acyl group which may be substituted, sulfonyl group which may be substituted or triazinyl group which may be substituted, particularly hydrogen atom.
R2 is preferably hydrogen atom, alkyl group (normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms) which may be substituted, phenyl group which may be substituted, acyl group which may be substituted, sulfonyl group which may be substituted or triazinyl group which may be substituted, more preferably alkyl group which may be substituted, phenyl group which may be substituted, acyl group which may be substituted, sulfonyl group which may be substituted or triazinyl group which may be substituted, particularly alkyl group or phenyl group which may be substituted. Further, these groups described as R2 may have azo groups with which may be connected to dyestuff residues. As the combination of R1 and R2 there is preferably used a combination of hydrogen atom as R1 and hydrogen atom, alkyl group or phenyl group which may be substituted as R2, most preferably combination of hydrogen atom as R1 and alkyl group or phenyl group which may be substituted as R2.
In the aforementioned description, the substituents which R1 and R2 further have thereon are not specifically limited. In the case where the group to be substituted is an alkyl group, it is substituted by a substituent normally having from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms. In the case where the group to be substituted is a group other than alkyl group, it is substituted by a substituent normally having from 1 to 15 carbon atoms, preferably from 1 to 10 carbon atoms.
Specific examples of R1 and R2 include methyl group, ethyl group, 2-hydroxyethyl group, 2-carboxyethyl group, phenyl group, 3-sulfophenyl group, 4-carboxyphenyl group, acetyl group, benzoyl group, 4-methylphenylsulfonyl group, 3-bis(2-hydroxyethyl)amino-5-(2-sulfoethyl)amino-2,4,6-triazino group, etc. in addition to hydrogen atom.
As m, n, p and q there may be used arbitrary numbers falling within the aforementioned range. It is particularly preferred that m be 0, n be 1 or 2 and p be 1. In particular, q is preferably 1, that is, the dyestuff of the general formula (1) is preferably a trisazo compound having three azo groups per molecule.
As M, too, there may be selected an arbitrary metal, preferably a divalent or trivalent transition metal such as copper, nickel, iron and cobalt.
The dyestuff of the present invention can be preferably used as a dyestuff for black recording liquid. In order to apply the dyestuff of the present invention to a recording liquid, it may be used in the form of free acid represented by the general formula (1). Alternatively, the acid group may be partially or entirely converted to a desired salt form before use. As the counter ion constituting the salt there may be used one or more ions selected from the group consisting of alkaline metal ions such as lithium, sodium and potassium ions, ammonium ion, and substituted amines. Specific examples of the substituted amines include mono-, di- and tri-substituted amines the substituent on which is alkyl group having from 1 to 4 carbon atoms and/or hydroxyalkyl group having from 1 to 4 carbon atoms. Different counter ions may be used in combination.
As the dyestuff represented by the general formula (1) or (1xe2x80x2) to be used in the recording liquid of the present invention there may be exemplified as a preferred specific example a compound the A to D moieties of which are selected from the following groups and are combined with one another.
Examples of A include the structures represented by the following formulae (A-1) to (A-12). Preferred among these structures are (A-1), (A-6), (A-8) and (A-10). 
Examples of B include the structures represented by the following formulae (B-1) to (B-10). Preferred among these structures are (B-1), (B-3) and (B-8). 
Examples of C include the structures represented by the following formulae (C-1) to (C-4). Preferred among these structures are (C-1) and (C-2). 
Examples of the aromatic compound having D as a partial structure include those represented by the following formulae (D-1) to (D-14). Preferred among these compounds are aromatic compounds represented by the formulae (D-1), (D-2), (D-7), (D-8) and (D-10). 
Still desirable specific examples of the dyestuff to be used in the recording liquid of the present invention will be shown in Table 1 below, but the present invention is not limited thereto.
The recording liquid or recording liquid for inkjet of the present invention contains an aqueous medium and at least one metal chelated azo dyestuff represented by the general formula (1) or salt thereof. Two or more of the compounds represented by the general formula (1) may be used in combination in the recording liquid. The content of the dyestuff of the general formula (1) in the inkjet recording liquid is preferably from about 0.5% to 10% by weight, particularly from about 2% to 7% by weight based on the total weight of the recording liquid.
The black metal chelated azo dyestuff the free acid form of which is represented by the aforementioned general formula (1) gives a desirable achromaticity itself but may be slightly bluish, greenish, reddish or purplish. In order to further improve the achromaticity, other water soluble dyestuffs (hereinafter referred to as xe2x80x9ccomplementary dyestuffsxe2x80x9d) can be further used as complementary components to prepare recording liquid, thereby obtaining a printed image having a more proper tone and a desirable light-fastness in the present invention.
Further, in the present invention, even when the recording liquid further containing the aforementioned complementary dyestuffs comprises as a black metal chelated azo dyestuff a dyestuff represented by the aforementioned general formula (1) wherein q is 0, a printed image having a proper tone and a desirable light-fastness can be obtained. In the specification of the present application, the black metal chelated azo dyestuff which is a disazo compound wherein q is 0 or a polyazo compound having more azo groups is defined by the aforementioned general formula (8). Accordingly, the dyestuff represented by the general formula (8) is the same as the aforementioned general formula (1) except that it includes those of the general formula (1) wherein q is 0. In other words, M1, A1, B1, C1, D1, m1, n1 and p1 in the general formula (8) have the same meaning as that of M, A, B, C, D, m, n and p in the general formula (1). This applies also to specific preferred examples. Further, R13 and R14 in the general formula (8) have the same meaning as R1 and R2 in the general formula (1). This applies also to specific preferred examples. q1 preferably indicates an integer of from 1 to 3, more preferably 1.
As the complementary dyestuff to be used in the aforementioned recording liquid for inkjet there may be used a water soluble dyestuff which can be generally used as an inkjet recording dyestuff without any restriction so far as the effect of the present invention can be exerted. Azo dyestuffs and non-azo dyestuffs may be used. Preferred among these dyestuffs are azo dyestuffs. The black metal chelated azo dyestuff to be used in the present application may be present in the form of azo dyestuff which is not fully complexed due to its properties. However, in the present application, the incorporation of a water soluble dyestuff for toning in addition to the black metal chelated azo dyestuff is included in the scope of the present invention. As such a water soluble dyestuff for toning there is preferably used a dyestuff which is not in the form of metal complex besides the metal complex dyestuff. As far as the metal complex of the present invention has properties such as sufficient light-fastness, the auxiliary use of a small amount of a water soluble dyestuff which is not in the form of metal complex makes it possible to obtain sufficient properties.
Examples of the azo dyestuff among the dyestuffs to be used as complementary dyestuff of the present invention include monoazo dyestuff, disazo dyestuff, trisazo dyestuff, etc. The skeleton of the azo dyestuff to be used as complementary dyestuff may be the same as or different from that of the general formula (8), preferably different from that of the general formula (8). The aromatic ring constituting these dyestuffs may have heteroatoms. In some detail, dyestuffs having a basic skeleton set forth in Table 2 below, etc. are preferably used. R in the general formulae in Table 2 each indicates a hydrogen atom, halogen atom or any other arbitrary substituent or may be a substituent including the dyestuff structure in the respective general formula. In the case where there are a plurality of R""s in the general formulae, they may be the same or different.
More specifically, as the complementary dyestuff there is preferably used, e.g., a water soluble dyestuff the free acid form of which is represented by any of the following general formulae (2) to (5): 
(wherein E represents phenyl group which may be substituted or naphthyl group which may be substituted; R3 represents hydrogen atom, halogen atom, alkyl group having from 1 to 4 carbon atoms, alkoxy group having from 1 to 4 carbon atoms, carboxyl group or sulfonic acid group; R4 represents carbonyl group or triazinyl group which may be substituted; L represents an arbitrary connecting group; and r represents 0 or 1, with the proviso that a plurality of E""s, R3""s and R4xe2x80x2 which are present in the molecule each may be the same or different), 
(wherein R5 represents hydrogen atom, alkyl group having from 1 to 4 carbon atoms, acyl group or triazinyl group which may be substituted; and E represents phenyl group which may be substituted or naphthyl group which may be substituted), 
(wherein E represents phenyl group which may be substituted or naphthyl group which may be substituted; R4 represents carbonyl group or triazinyl group which may be substituted; and L represents an arbitrary connecting group), 
(wherein R6 represents triazinyl group which may be substituted; and R7 represents hydrogen atom, halogen atom, alkyl group having from 1 to 4 carbon atoms, alkoxy group having from 1 to 4 carbon atoms, carboxyl group or sulfonic acid group).
Examples of the non-azo dyestuff among the complementary dyestuffs include condensed ring compounds such as dioxazine-based, anthraquinone-based, xanthene-based, anthrapyridone-based and metal phthalocyanine-based condensed ring compounds. As the complementary dyestuff there may be used a metal chelated dyestuff other than metal chelated dyestuff of the present invention, preferably metal chelated azo dyestuff.
Specific examples of the anthrapyridone-based dyestuff include an anthrapyridone-based water soluble dyestuff the free acid form of which is represented by the following general formula (6): 
wherein in the general formula (6) R8 represents hydrogen atom, halogen atom, cyano group, alkyl group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted, alkoxy group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted, alkoxycarbonyl group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted or acyl group which may be substituted; R9 represents hydrogen atom, alkyl group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted or alkoxy group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted; R10 represents hydrogen atom, alkyl group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted, alkoxy group (preferably having from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms) which may be substituted or phenoxy group which may be substituted; and R11 represents hydrogen atom, halogen atom, amino group which may be substituted or anilino group which may be substituted.
Specific examples of the aforementioned metal chelated azo dyestuff include a metal chelated azo dyestuff formed by an azo compound the free acid form of which is represented by the following general formula (7) and a metal element: 
wherein in the general formula (7) X1 and X2 each independently represents a plurality of atoms required to form at least one 5- to 7-membered aromatic ring, with the proviso that the aromatic rings containing X1 or X2 each may have substituents, the substituents on the aromatic rings may be further condensed to form condensed rings and the aromatic rings containing X1 or X2 may contain heteroatoms; R12 represents hydroxyl group, carboxyl group, sulfonic acid group, phosphono group, alkyl group (preferably having from 1 to 6 carbon atoms), alkoxy group (preferably having from 1 to 6 carbon atoms) or amino group which may be substituted; and s represents an integer of from 1 to 5, with the proviso that if there are a plurality of R12""s, they may be the same or different.
As the metal element which forms a chelate with the aforementioned azo compound there is preferably used a divalent or trivalent transition metal, more preferably copper, nickel, iron or cobalt, particularly copper or nickel.
As the metal in the metal phthalocyanine dyestuff there may be used a divalent or trivalent metal, preferably divalent or trivalent transition metal, more preferably copper, nickel, iron or cobalt, particularly copper or nickel.
In the general formulae (3) to (7), the substituent which may be substituted is not specifically limited but is a substituent which may be substituted by a substituent preferably having from 1 to 20 carbon atoms, more preferably from 1 to 15 carbon atoms. In the general formulae (3) to (7), the substituent which may be substituted is preferably one having from 1 to 6, preferably from 2 to 6 hydrophilic groups such as carboxyl group, sulfonic acid group and phosphono group per dyestuff molecule.
Specific examples of the aforementioned complementary dyestuff include C. I. Acid Yellow 17:1, C. I. Acid Yellow 23, C. I. Acid Yellow 49, C. I. Acid Yellow 65, C. I. Acid Yellow 104, C. I. Acid Yellow 155, C. I. Acid Yellow 183, C. I. Acid Yellow 194, C. I. Direct Yellow 86, C. I. Direct Yellow 106, C. I. Direct Yellow 132, C. I. Direct Yellow 142, C. I. Direct Yellow 173, D. I. Direct Yellow 194, C. I. Acid Red 8, C. I. Acid Red 37, C. I. Acid Red 50, C. I. Acid Red 51, C. I. Acid Red 52, C. I. Acid Red 87, C. I. Acid Red 92, C. I. Acid Red 93, C. I. Acid Red 95, C. I. Acid Red 98, C. I. Acid Red 287, C. I. Acid Red 35, C. I. Reactive Red 23, C. I. Reactive Red 180, hydrolyzate of C. I. Reactive Red 180, C. I. Direct Violet 107, C. I. Acid Blue 9, C. I. Hood Black 2, C. I. Direct Black 19, C. I. Direct Black 154, C. I. Direct Black 195, C. I. Direct Black 200, C. I. Direct Blue 86, C. I. Direct Blue 199, and dyestuffs the free acid form of which is represented by the structural formula exemplified in Table 3.
In order to prepare the recording liquid of the present invention, the black metal chelated azo dyestuff represented by the general formula (8) and the complementary dyestuff may be used in the form of free acid. However, the acid group may be partially or entirely converted to a desired salt form before use. As the counter ion constituting the salt there may be used one or more ions selected from the group consisting of alkaline metal ions such as lithium, sodium and potassium ions, ammonium ion, and substituted amines. Specific examples of the substituted amines include mono-, di- and tri-substituted amines the substituent on which is alkyl group having from 1 to 4 carbon atoms and/or hydroxyalkyl group having from 1 to 4 carbon atoms. Different counter ions may be used in combination.
The black metal chelated azo dyestuffs represented by the general formulae (2) to (8) and complementary dyestuffs each preferably have a molecular weight of not greater than 5,000, particularly not greater than 2,000.
The content of the dyestuff of the general formula (8) in the recording liquid of the present invention is preferably from 0.5% to 10% by weight, particularly from 2% to 7% by weight based on the total weight of the recording liquid, and the content of the other complementary dyestuffs in the recording liquid is preferably from 0.2% to 3% by weight, particularly from 0.5% to 2% by weight based on the total weight of the recording liquid. Referring to the weight proportion of the black dyestuff of the general formula (8) and the complementary dyestuff in the recording liquid, the proportion of the complementary dyestuff is preferably from 0.02 to 0.3, more preferably from 0.05 to 0.15 per black metal chelated azo dyestuff of the general formula (8).
In general, in order to improve the achromaticity of the black metal chelated azo dyestuff, the complementary dyestuff is used in a weight proportion of from 0.2 to 0.3 per black metal chelated azo dyestuff. In the case where black metal chelated azo dyestuffs having different hues are mixed for toning, the mixing ratio thereof may be 1:1. As previously mentioned, such a complementary processing have often led to the deterioration of light-fastness of the image obtained.
Nevertheless, the recording liquid of the present invention shows no deterioration of light-fastness even when subjected to toning. The presumable reason for this phenomenon is that the dyestuff represented by the aforementioned general formula (8) itself has a sufficiently improved light-fastness as compared with the conventional dyestuffs as well as a sufficiently improved achromaticity, exerting a synergistic effect with the resulting reduction of the amount of toning dyestuffs to be added to obtain a sufficiently good achromatic image from the conventional case.
The recording liquid preferably contains as a solvent water and a water soluble organic solvent such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (#200), polyethylene glycol (#400), glycerin, N-methylpyrrolidone, N-ethylpyrrolidone, 1,3-dimethylimidazolidinone, thiodiethanol, dimethyl sulfoxide, ethylene glycol monoallyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, 2-pyrrolidone, sulfolane, ethyl alcohol and isopropanol. These water soluble organic solvents are normally used in an amount of from 1 to 50% by weight based on the total amount of the recording liquid. On the other hand, water is used in an amount of from 45% to 95% by weight based on the total amount of the recording liquid.
The recording liquid of the present invention may contain a compound selected from the group consisting of urea, thiourea, biuret and semicarbazide incorporated therein in an amount of from 0.1% to 10% by weight, preferably from 2% to 8% by weight based on the total amount of the recording liquid or a surface active agent incorporated therein in an amount of from 0.001 to 5.0% by weight based on the total amount of the recording liquid to further improve the quick-drying properties of the b image which has been printed and the print quality.
The recording liquid of the present invention can be used for writing utensils or inkjet recording and is particularly suitable for inkjet recording. When recorded on ordinary paper, the recording liquid of the present invention can provide a black recorded matter having an excellent print density and fastness. The recording liquid of the present invention is excellent also in light-fastness on glossy paper and glossy film for use in photography, etc. The recording liquid of the present invention also has a good storage stability.